(1) Field of the Invention
The present invention relates to digital telephone switching and more particularly to a digital concentrator for use with a digital telephone office. The digital concentrator allows the number of subscriber stations connected to a T1 line to exceed the capacity of the T1 line based on the probability of occurrence of simultaneous requests for service. Remote subscriber stations are thus provided with the full range of customer features associated with a digital telephone office. Thus an economical means is provided for connecting remote subscriber stations to a class 5 telephone office.
(2) Description of the Prior Art
Concentration systems are old and well known. Typically they require a concentrator located near the subscriber stations and an expander located in a central office. Such concentrators and expanders are of an analog nature and require one appearance on the output of the expander for each appearance on the input of the concentrator. Thus the connection between these subscriber stations and the telephone office are minimized, but such an arrangement requires the use of an expansion stage. Further, such analog concentration systems are not adaptable to digital telephone offices unless the analog signals from the output of the expansion stage are converted to digital format for use by the digital telephone office.
Accordingly, it is an object of the present invention to provide a digital concentrator which can be connected directly to a digital telephone office without the use of an expansion stage or an analog to digital interface.